On January 4, 2020, about 1600 central standard time, an Aero Commander 100 airplane, N5573M, sustained substantial damage when it was involved in an accident near Mullin, Texas. The student pilot and flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The flight instructor reported that he and the student departed on the 75-nautical-mile flight with 40 gallons of fuel onboard. About 3 miles from the destination airstrip, they initiated a slow descent to a private airstrip. The student completed the Descent and the Before Landing checklist. About 3,000 ft above mean sea level, the engine lost total power.

The instructor immediately took control of the airplane and ensured that the fuel selector switch was selected for both fuel tanks, the carburetor heat was applied, and the mixture control was at the full-rich position. He trimmed the airplane for its best glide speed and the student completed a mayday call. The instructor switched fuel tanks; however, the engine did not respond, and the propeller was “wind milling.” The instructor performed a forced landing to a flat, plowed dirt field, during which the right wingtip impacted a tree and the airplane nosed over.

The airplane sustained substantial damage to the fuselage, both wings, and the empennage. The fuel system was breached during the accident and the exact amount of fuel onboard at the time of the loss of engine power could not be determined. The airplane was recovered from the accident site and an engine run was performed. The engine successfully ran for several minutes at various power settings when a fuel source was plumbed to the engine. No mechanical anomalies were found during the engine run.

Examination of the fuel selector revealed that either the fuel selector handle or the pointer was installed 180° out of position. When the selector handle was selected to BOTH, the valve was completely closed, in what should have been the OFF position. When the selector handle was selected to OFF, the valve was open, in what should have been the BOTH position. The hole on the end of the pointer that slid over the shaft featured a round side and a flat side, which helps to correctly orient the pointer during installation. The hole was sufficiently worn that the pointer would fit over the shaft in both directions. The examination could not determine if the selector handle or the pointer was installed incorrectly.

The temperature and dewpoint for the accident time and accident site were not conducive to the formation of carburetor icing.